1. Field of the Invention
The present invention relates to a light shielding structure of a zoom lens barrel.
2. Description of the Related Art
In conventional zoom lens barrels, it is common practice to linearly guide lens frames, which support lens groups, in an optical axis direction by a linear guide mechanism. Although various types of such linear guide mechanisms have been proposed, it is basically the case that a set of linear guide grooves which extend parallel to an optical axis are formed on a stationary member while a set of followers which are respectively engaged in the set of linear guide grooves are formed on a movable member (e.g., a movable lens frame).
In zoom lens barrels produced in recent years, there has been a growing tendency for the aforementioned set of linear guide grooves to be formed as a set of linear guide slots (through-slots) for the purpose of miniaturizing the zoom lens barrel, especially for reducing the diameter of the zoom lens barrel. However, using such through-slots raises a possibility of harmful light such as stray light entering into an optical path of the zoom lens barrel through the linear guide slots, and hence, reaching the picture plane (e.g., an imaging surface of an image pickup device or a sensitive surface of silver-salt film). Specifically, since the relative position of a plurality of lens frames varies in a zooming operation, harmful light which has nothing to do with the photographing operation may reach the picture plane through the set of linear guide slots in some specific relative position of the plurality of lens frames to impair an obtained object image. To prevent this problem from occurring, it is common practice to provide a light shielding structure for preventing such harmful light from entering into an optical path of the zoom lens barrel to reach a picture plane. However, it is difficult to obtain a simple light shielding structure which is effective over the entire zooming range because the relative position of the plurality of lens frames in the optical axis direction varies in a zooming operation.